docs: def extract_fieldnames(config):
      """
      Function to return a list of unique field names from the config file
  
      :param config: The configuration file that contains the specification of the extractor
      :return: A list of field names from the config file
  
      """
      fields = []
      for x in get_fields(config):
          if x in fields:
              fields.append(x + '_' + str(fields.count(x) + 1))
          else:
              fields.append(x)
      return fields